Wiring current drop problems

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  #1  
Old 02-01-14, 10:15 AM
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Wiring current drop problems

Hi I want hel with this problem can I use THHN-CPR 8 wire to install a new pump 250ft long inside underground conduit pipe the pump is 230 V
 
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Old 02-01-14, 10:44 AM
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What are the ampacity requirements for the pump?
 
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Old 02-01-14, 10:48 AM
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If you are installing wiring outside in conduit it needs to be water rated. You need to see THWN or THWN/THNN on the wire. #8 is pretty big wire for a pump but will work well at that distance.
Do you know how much current the pump draws ?

You didn't mention what type of pump so I'm assuming it's a submersible pump in a deep well. The THWN is run to the top of the casing. You need to use special wire to actually go down the well to the the pump itself.
 
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Old 02-01-14, 12:00 PM
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Thank you for your time the pump is a 4" sumersible deep well 230 V -6.8 A max
 
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Old 02-01-14, 12:16 PM
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#12 copper would be fine for that amount of current. Voltage drop would be limited to 2.32% @ 7 amps.

Read your pump manual, some pumps require 3 wires, plus a ground, run to them.
 
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Old 02-01-14, 12:55 PM
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Just for info the deep well is 150 ft,the problem is that the well is away from the panel 250ft
 
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Old 02-01-14, 01:48 PM
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the deep well is 150 ft,the problem is that the well is away from the panel 250ft
Are you saying that it's 250' from your panel to your well head and another 150' down to your submersible pump, making it 400' total from the panel to the load?
 
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Old 02-01-14, 03:43 PM
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While voltage drop is referenced in the code as an informational note, it is not a requirement. The recommendation of the NEC is 3% for branch circuits and 5% for feeders. (your pump circuit is a branch circuit)

At 400' total, 6.8 amps on #12 copper the voltage drop is 3.6%.

At 400' total, 6.8 amps on #10 copper the VD would be 2.6%
 
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Old 02-01-14, 09:07 PM
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Sure

It sound a little confuse but we going to run the wire from the main panel to the little box for the submersible pump,distance is 250 ft ,then installing the pump will be another 150 ft deep inside 5" pipe. I think it is thinner than the 8 awg main that Im thinking put from the panel
 
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Old 02-01-14, 09:13 PM
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I think it is thinner than the 8 awg main that Im thinking put from the panel
It probably is thinner than 8AWG. As Tolyn said or implied earlier, you might get away with running 12AWG but 10AWG is what you should use. Either way, you don't need 8AWG.
 
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Old 02-01-14, 09:41 PM
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A little draw to help moreug

This is a little draw to understand how it is
 
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Old 02-01-14, 09:51 PM
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Ok ty for help I need to check a little more the amps needing for pump to be sure alsois a good idea to use thegrey pvc conduit like 3/4 ?
 
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Old 02-02-14, 06:10 AM
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Yes, you have to use electrical PVC, the gray stuff. For that long of pull I would suggest going with 1". If you do go with #10 make sure to use THWN stranded wire. Solid will be quite hard to pull.
You are going to need to pull in a ground (green) as well since you are using PVC. #12 will be fine for that.
 
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Old 05-28-14, 08:48 PM
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Can I use thhn/thwn-2 wire?
 
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Old 05-28-14, 09:02 PM
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As long as there is a W in the rating for wet locations.
 
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Old 05-29-14, 04:33 AM
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You are going to need to pull in a ground (green) as well since you are using PVC. #12 will be fine for that.
Save yourself or someone else a headache and pull #10 EGC in case you ever change plans and put a 30A breaker on those #10 conductors. If plans change (bigger pump later) then 250.122 dictates otherwise.
 
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Old 05-30-14, 12:30 AM
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Pump Wiring

If you are installing the conductors from the well head to the pump (150ft), don't forget to install cable guards to keep the discharge piping from hitting the conductors when the pump starts. The well supplier should be able to provide those for you. They usually go about 15ft above the pump and then one every 25ft up to the well head. There should also be a torque arrestor located just above the pump. Conductors in the well casing will be submersible rated and not the THHN/THWN that you run to the well head. Submersible rated conductors are rated to be in water continuously for the life of the pump. The manufacture of your pump should have a chart that will give you the minimum conductor size for the HP rating of your pump.
 
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